The first and second panel are a discussion between Megan and Ponytail about dreams. Megan mentions a dream or nightmare about failing to prepare for an exam, despite not being a student for years. This is similar to the dream depicted in 557: Students. Ponytail responds that certain dreams occur with surprising frequency among many people, dubbing them "Universal Dreams" (which is the title of the comic). Universal dreams are dreams that are weirdly common, as also abused in 719: Brain Worms.

In the third panel, Black Hat describes an avatar of misfortune in the form of a horse appearing on a hill. This could be a play on the word nightmare. A mare was originally a demon or goblin that gave bad dreams. The modern word mare, meaning female horse, has a different origin, but still serves handily as a homophonic pun.

Alternatively, this may be a reference to the 2007 film Michael Clayton, which features a dreamlike sequence where the title character recognizes a scene of three horses on a hilltop from an illustration in a book. He stops his car, gets out and approaches the horses, just minutes before his car explodes. This marks a major turning point in the direction Clayton takes for the rest of the film, similar to how Black Hat says "[the horses] mean the dream is about to turn bad."

In the last panel, Black Hat describes having dreams where he receives specific information about the real world, which seems closer to prophesying or precognition than what would be considered a normal dream, as normal dreams do not tell the future.[citation needed] This may be a reference to the 2009 film Knowing, in which a child hears voices telling her the date, time, latitude, and longitude of major disasters (including earthquakes) that will occur 50 years in the future.

In the title text, either Megan or Ponytail is responding to Black Hat when she unexpectedly interrupts herself with the first part of geographic coordinates (Latitude 35), just as Black Hat described, implying that the whole comic might be another of Black Hat's dreams. 35 degrees North would include 31 major cities around the world, including 11 in Japan and 8 in the USA (including California, a seismically active region); the only major city within 35 degrees South is Canberra, Australia. This would suggest that an earthquake would happen soon in one of those major cities. The second half of the coordinates are most likely cut off to add uncertainty to the situation.

Dreaming of latitude and longitude was also a topic of 240: Dream Girl, but in contrast to this comic, the events in that dream did not come true within the comic. (However, a real-life meetup of xkcd fans occurred at the location and date mentioned within the comic.)

"This suggest an earthquake would happen soon in one of those major cities". Why? It's not hollywood, earthquakes can happen even in unpopulated areas. 172.68.54.70 17:38, 17 January 2018 (UTC)

Earth quakes that influence few people are less likely to appear in global news and be confirm-able as the comic implies.162.158.74.27 00:42, 18 January 2018 (UTC)

Black Hat would probably confirm the existence of earthquakes by checking websites like [1] instead of mass media. Also there is nothing in the comic about the earthquakes being major ones; seismometers can detect quakes that are too weak to be noticed by people even if they happen to be directly above the center of the quake, and since such tiny quakes are much more common than big ones, and since Black Hat implies this is a frequent dream for him, it isn't plausible that he would only dream about quakes that are above the news threshold. 162.158.238.172 10:23, 18 January 2018 (UTC)

I agree completely; It seems not only presumptuous, but rather illogical to suggest that the alt-text would only be referring to major cities. If he's had the dreams often, it makes more sense to assume that he's coming up with coordinates for every major earthquake, regardless of it's location. My question is, have there been any major earthquakes in that zone since the comic was published? If so, we should mention that, as it adds amusing weight to the prophecy theme.

I love the [Citation Needed] tag on the line about dreams. 172.68.143.132 18:20, 17 January 2018 (UTC)

Thanks, although the jokes are funny, poking a little fun at wikipedia's super serious style, I feel they are a little overused. Nonetheless I still add them occasionally... 108.162.219.214 23:00, 17 January 2018 (UTC)

Well, I hadn't noticed that someone took it out, when I put one in. I'm not joking though: In all seriousness, aren't dreams about the future exceedingly common? I find the blanket statement that normal dreams don't do that to be very strange & potentially unfounded. I want to see some references backing up that assertion. ProphetZarquon (talk) 23:52, 18 January 2018 (UTC)

Non-expert and no references, but I find dreams are more about memories - either my own experiences or things I recently saw on TV - and not the future. Which your brain doesn't know how to fill in. And the proposition is of dreams telling you what will happen in the future, but a normal dream about the future would be a guess; a prophetic dream, like in Shakespeare or the bible, is special. My explanation though is that Black Hat leaves World Service radio on at night, and radio news about earthquakes is incorporated in his dreams. Or he has an internet smart speaker which is programmed to do that. He knows what happened because he was already told. Robert Carnegie [email protected]162.158.34.82 00:32, 19 January 2018 (UTC)

Hm. If premonitory dreams are special, then about 60% of the dreams which I remember upon waking are special. Most of my dreams seem to be my brain trying to predict future events based upon my memories of that week. Half the rest are dreams that I'm flying, or following someone, & the rest are mostly dreams about work. A lot of my prophetic dreams do eventually come true, but I don't think I'm prescient or anything; I just figure that life is more predictable than we tend to feel it is. ProphetZarquon (talk) 19:15, 24 January 2018 (UTC)

I...did not expect the comic to go that direction. When the first half of the comic loaded (my internet's kinda unreliable right now), I thought "This is probably going to be something questioning how universal these dreams are, and the fourth panel will be some caveman or something talking about its dream taking an exam and everyone will be confused." But no, it was more...surreal.
I guess this is why Randall's the comic author and I'm not... 162.158.74.201 03:32, 18 January 2018 (UTC)

Thanks! Are these relevant enough to be added to the explanation of the zone defined (incompletely) in the alt-text? ProphetZarquon (talk) 23:52, 18 January 2018 (UTC)

Thanks for that URL, it made my iPad zoom WAY out on the whole page to fit it on as few LONG lines as possible, LOL! (Just makes me wonder how many of those codes could just be replaced with the normal characterr). NiceGuy1 (talk) 04:21, 19 January 2018 (UTC)

Was thinking the same thing... both his books (Which I got for Christmas :P) both mention him living in Massachusetts on the cover. Thing explainer, the most recent book was released in 2015. I would assume he hasn't moved since then. Linker (talk) 13:13, 18 January 2018 (UTC)